1. Field of the Invention
The present invention relates to a data control apparatus, and more particularly to a data transmission control apparatus in which input/output units are commonly used by plural central processing units.
2. Related Background Art
In conventional systems, for example an image processing system, each central processing unit (CPU) is often equipped with at least an image input unit such as an image reader or an image output unit such as an image printer. However, in such a system, the proportion of use of such image input/output units is quite low in the entire processing time of the system, and the connection of an expensive image input/output unit to each CPU is very inefficient. For this reason there has been proposed a system which is provided with a printer control unit, called a printer server, by means of which a printer unit is commonly utilized by plural CPU's through a local area network (LAN). However such a system involves a complicated LAN and common control and is not suitable for a small system.